This application is a 35 USC 371 application of PCT/DE 01/04631, filed on Dec. 8, 2001.
1. Field of the Invention
The invention is directed to an improved flap valve for controlling a gas flow in a gas flow system of an internal combustion engine.
2. Description of the Prior Art
In a known disposition of a throttle valve in an exhaust system of an internal combustion engine (German Patent Disclosure DE 43 05 123 A1), the valve shaft, which carries the throttle valve and extends parallel to the valve plane, is guided on both sides by a bearing bore in the conduit wall of the exhaust system and protrudes through one bearing sleeve on each side. To achieve greater tightness while avoiding sluggishness of the valve actuation, the bearing sleeves, axially prestressed by spring force each in a respective bearing housing, are radially displaceable within the bearing housings, thus automatically compensating for dimensional differences between stop faces, formed on the conduit wall, for the throttle valve and the valve shaft bearing upon first closure of the throttle valve.
In German Patent Disclosure DE 199 34 113.3, which had not yet been published by the priority date of the present application, it has already been proposed that a flap valve of the type defined at the outset be used as an exhaust gas recirculation valve for the metered admixture of exhaust gas with the aspirated fresh air in the intake system of an internal combustion engine. In this case, an opening into which the flap valve is inserted with its valve outlet in gastight fashion, is provided in the jacket of an intake tube of the intake system. The valve flap, with a valve shaft positioned obliquely to the valve plane, is disposed in a thin-walled tube for the sake of flap adjustment; the thin-walled tube rests with radial play in the rigid valve tube and is secured by one tubular portion to the valve tube. By suitable shaping of the valve flap, the valve flap in its closing position conforms to the inner wall of the elastic thin-walled tube and closes off the tube cross section in gastight fashion, so that a separate seal between the valve tube and the valve flap can be dispensed with.
The flap valve of the invention has the advantage that the valve tube and the thin-walled tube can be produced economically, especially if, in accordance with an advantageous embodiment of the invention, they are injection-molded of plastic. With injection molding technology, it is unproblematic to vary the wall thickness and the tube length of the integrally formed-on thin-walled tube and thus to adapt the elasticity, required for the tightness of the flap valve, of the thin-walled tube to the thin-walled tube diameter. The elastic thin-walled tube, in the closing state of the valve flap, conforms tightly to the valve flap, so that stringent demands for tightness, of the kind made for control valves for internal combustion engines, especially in a throttle valve for an aspirating engine, can be met quite well without entailing major production cost and without making stringent demands in terms of the precision of production. Because of the oblique position of the valve shaft to the plane of the valve flap solidly connected to it, on the one hand the required leadthroughs in the valve shaft in the valve tube are located outside the thin-walled tube, so that critical sealing problems do not arise in the closing region, and on the other, greater sensitivity in the adjustment of the flap valve is achieved, since the requisite rotary angle range of the valve shaft between the closing position and the maximally open position of the valve flap increases, in fact to an increasing extent as the positioning angle becomes greater.
In one advantageous embodiment of the invention, a connection collar is embodied on one end of the valve tube, which collar surrounds the thin-walled tube with radial spacing and protrudes axially past the free end of the thin-walled tube. As a result of this structural provision, on the one hand simple integration of the elastic thin-walled tube into the valve tube is possible, and on the other, easy unmolding of the valve tube in the injection molding process is assured. Preferably the inside diameters of the valve tube and the thin-walled tube are equal, while the connection collar has an inside diameter greater than the outside diameter of the thin-walled tube.
In a preferred embodiment of the invention, the flap valve serves to control the air aspirated in the intake system of an internal combustion engine; the valve flap forms the throttle valve, which is actuated by a rotary drive mechanism, and the valve tube, in the form of a so-called throttle valve neck, is integrated into the throttle valve housing. By the positioning of the axis of the valve shaft relative to the plane of the valve or the throttle valve, sealing problems that occur in conventional throttle valve controllers because of the leadthrough of the valve shaft in the throttle valve neck, are eliminated; this is because in the flap valve of the invention, because of the oblique position of the valve shaft, the valve shaft indeed penetrates the valve tube or throttle valve neck, but does not penetrate the thin-walled tube that assures the tightness of the flap valve. The leadthrough in the valve tube and in the throttle valve neck can be sealed off without problems. Moreover, because of the angular position of the valve shaft to the plane of the throttle valve, small-quantity metering near the closing range of the throttle valve is improved substantially, so that during engine idling, for the same gear ratio of the rotary drive mechanism, especially sensitive controllability of the throttle valve and thus of the aspirated air quantity is achieved.